High lubricity corrosion resistant threaded fastener and method

ABSTRACT

A METHOD OF PREPARING A HIGH LUBRICITY CORROSION RESISTANT THREADED FASTENER OF OTHER COATED SUBSTRATE PRODUCT COMPRISING THE STEPS OF: (A) CLEANING THE SUBSTRATE, FOR EXAMPLE IN A SOAP BATH, (B) WATER RINSING, (C) APPLYING AN AQUEOUS ACIDIC METALLIC PHOSPHATE COATING SOLUTION TO THE SUBSTRATE, (D) APPLYING A CORROSION RESISTANT OIL TO THE SUBSTRATE, AND (E) APPLYING A MIXTURE OF SOLID LUBRICANT PARTICLE DISPERSION AND WATER SOLUBLE CORROSION RESISTANT OIL TO THE SUBSTRATE; AND, THE COATED PRODUCT FORMED BY THE ABOVE METHOD.

United States Patent O 3,573,111 HIGH LUBRICITY CORROSION RESISTANTTHREADED FASTENER AND METHOD Raymond L. Thurston, Dearborn, Mich.,assignor to Microdot Inc., Greenwich, Conn. N Drawing. Filed Sept. 6,1968, Ser. No. 774,555 Int. Cl. C23f 7/10 US. Cl. 148--6.15 8 ClaimsABSTRACT OF THE DISCLOSURE A method of preparing a high lubricitycorrosion resistant threaded fastener or other coated substrate productcomprising the steps of: (a) cleaning the substrate, for example in asoap bath, (b) water rinsing, (c) applying an aqueous acidic metallicphosphate coating solution to the substrate, ((1) applying a corrosionresistant oil to the substrate, and (e) applying a mixture of solidlubricant particle dispersion and water soluble corrosion resistant oilto the substrate; and, the coated product formed by the above method.

BACKGROUND OF THE INVENTION This invention broadly relates to a surfacetreatment for various substrate products wherein it is desired to impartto the substrate high lubricity and corrosion resistance, and forcertain applications the surface is also provided with highly desirablebreak-in allowance properties. The substrate products referred to arevarious types of fasteners such as threaded fasteners, slide mechanisms,bearings, or various mechanical components which are subjected to enginebreak-in wear. All of such substrates can be subjected to the surfacetreatment of this invention as disclosed hereinafter.

In the past, cadmium plating has frequently been used for fastenersurface treatment in order to provide the fastener surface withcorrosion resistance; and, also the cadmium plated fastener surface hasin the past been treated with wax to provide the cadmium plated fastenerwith high lubricity as well as corrosion resistance. The cadmium-waxfastener surfaces which have been so treated are generally bright andsilvery white in their appearance. The corrosion resistance of suchcadmiumwax treated fasteners is very good particularly when asupplemental chromate treatment of the fastener surface is made. Saltspray test results (ASTM test B-1l7-6l) on such cadmium treatedfasteners result in 96 hour plus salt spray exposure times. Thesecadmium treated fasteners also have been found to have a hardnessgreater than that of the substrate base material of the fastener.However, there has been a distinct and definite problem with thecadmium-wax treated fasteners and this problem has been one of aninordinately high cost of producing same. Accordingly, there has been along felt need in the art to develop a surface treated product or methodof producing same which would exhibit comparable or better corrosionresistance, and also comparable or better lubricity as compared to acadmium-wax surface treated substrate product, while at the same timesaid sought-after product had to be feasible of commercial productionand economical and readily capable of being produced.

Accordingly, it is a primary object of this invention to provide animproved surface treated product which possesses high lubricity andcorrosion resistance.

Patented Mar. 30, 1971 Another object of the present invention is toprovide a hightly lubricating composition which when applied in thesurface treatment of a substrate fastener product would greatly improvethe lubricity of the fastener, for example, a prevailing torque typefastener, while at the same time providing said fastener with maximum.corros1on resistance.

Another object of the present invention is to provide an improvedfastener product with the surface thereof possessing high lubricity andhigh corrosion resistance.

Another object of the present invention is to provide a method ofpreparing said improved fastener product.

Still another object of the present invention is to provide an improvedcoated substrate product, with the surface thereof possessing propertiesof high lubricity, corrosion resistance, and a surface which possessesdesirable break-in allowance properties; and, the method of preparingsaid improved coated substrate product.

Other objects, features and advantages of the present invention willbecome apparent from the subsequent description and the appended claims.

SUMMARY OF THE INVENTION The above and related objects, generallystated, are accomplished in conjunction with the solution of the problemunderlying this invention by the discovery that a substrate product maybe surface treated with a metallic phosphate coating to providecorrosion resistance then subsequently treated with a corrosionresistant oil to enhance the corrosion resistance, and then finallytreated with a mixture of a lubricant particle dispersion and corrosionresistant oil to thereby provide the surface with unique properties ofhigh lubricity in combination with high corrosion resistance.

The details of this invention will be more specifically describedhereinafter.

Briefly stated, this invention comprises a method of preparing a highlubricity, corrosion resistant, fastener or other coated substrateproduct comprising the steps of: cleaning the substrate, applying anaqueous acidic metallic phopshate coating solution to the substrate,applying a corrosion resistant oil to the substrate, and applying amixture of solid lubricant particle dispersion and water solublecorrosion resistant oil to the substrate, said lubricant being selectedfrom the group consisting of graphite, molybdenum disulfide, orvermiculite, said lubricant particle size being from about 0.5 to about200 microns, said dispersion containing between about 2% and about byweight total solids content, and said mixture containing a weight ratioof said dispersion to said oil between about 1:20 and about 20:1. From aproduct aspect this invention comprises a coated substrate productprepared in accordance with the method stated above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the exact theory ofoperation which underlies the invention is not exactly understood, andwhile it is not intended to limit the scope or application of theinvention by reliance on any particular theory of operation, it isbelieved that the phosphate coating which is applied to the substratesurface after application leaves small pores or openings in thephosphate coating or crystal structure which allow for absorption orreceipt of the corrosion resistant oil which is subsequently appliedthereto. Normally in the prior art after a phosphate coating has beenapplied, a sealing after-treatment is applied thereto generallycomprised of a chromic acid or mixed chromic and phosphoric acid rinse.However, in the present invention no such chromic acid or phosphoricacid sealing after-treatment is applied, rather and simply a corrosionresistant oil is first applied to the phosphate coated surface and it isbelieved that this corrosion resistant oil is absorbed or received intothe porous openings or crystalline openings of the phosphate coatedsurface without sealing off same. If the normal sealing after-treatmentwere applied subsequent to the phosphate coating, then porous openingsor the like, would be closed up. However, by first applying thecorrosion resistant oil which is absorbed into the porous openings thecorrosion resistance of the phosphate coating is enhanced. Furthermore,by subsequently applying a mixture (disclosed hereinafter) of alubricant particle dispersion and water soluble corrosion resistant oilto the oil treated surface, it has been discovered that this applicationof the mixture of lubricant particles and corrosion resistant oil isstill absorbed, or received into small openings or pores in thephosphate coating, to thereby impart to the phosphate coated surface ahigh lubricity coating which is also at the same time highly corrosionresistant. Still further, it has been found that if only a lubricantparticle dispersion is used as the last coating application to thesubstrate that then a satisfactory product is not obtained for thereason that the lubricant particle dispersion alone will not penetrateor leave a high lubricity surface finish on the substrate without thepresence of the corrosion resistant oil.

The cleaning of the substrate surface to carry out the method disclosedherein may be carried out in any conventional manner and for example,the cleaning of the substrate surface may be carried out by immersingthe substrate in a soap bath for a suflicient period of time and thencold water rinsing the substrate. Those skilled in the art will realizethat there are numerous different ways of properly cleaning thesubstrate such that it is ready for use in the method disclosed herein.

The metallic phosphate coating solution which is selected for use in themethod of this invention may satisfactorily be any aqueous acidicmetallic phosphate solution which is known to form a protectivephosphate coating on metallic surfaces and this includes coatingsolutions of zinc phosphate, manganese phosphate, iron phosphate, or thelike. Preferably, the phosphate coating solution which is aplied shouldbe of the zinc phosphate type.

Examples of typically suitable phosphate coating solutions for useherein are set forth below numbered as Examples 1, 2, 3, 4 and 5:

EXAMPLE 1 For the aqueous acidic metallic phosphate coating solution,the following solution would be used containing: 1% pounds zincphosphate, 3% pounds H PO pound of HNO A1 ounce of Ni(NO and the balancewater to make 100 pounds of solution.

This phosphate solution would be satisfactory for use at a temperatureof approximately 90 F.

EXAMPLE 2 A metallic phosphate coating solution containing the followingmaterials would be used: 22 grams per liter P 35 grams per liter N0 and19.5 grams per liter ZlIlC.

EXAMPLE 3 Aqueous acidic metallic phosphate coating solution would beused containing as follows: 11.5 grams per liter zinc, 14 grams perliter N0 and 13 grams per liter EXAMPLE 4 Aqueous acidic metallicphosphate coating solution would be used containing as follows: gramsper liter P 0 27 grams per liter zinc, 6 grams per liter C10 4 EXAMPLE 5An aqueous acidic manganese phosphate coating solution would be usedcontaining as follows:

Weight-grams MI1(H2PO4)2'2H2O HNO (42 Baum) 3.00 NaNOg 10.90 NaHF 0.90 KTiF 2.10 Water 94.9

Total 1 191.8

1 133 ml. v01.

A particularly preferred phosphate coating solution would be an aqueouszinc-iron phosphate solution such as Phosphotex A-8 available from theMacDermid Chemical Company of Waterbury, Conn. Phosphotex A-8 containsan acid ratio between 5 and 7, that is, a ratio determined from thetotal acid divided by the free acid; and, a ferrous iron content of 0.1to about 0.7% by weight; and, a zinc content of 0.20% by weight minimum.

The time period of application for the phosphate coating solution shouldbroadly be within the range of about /2 up to 120 minutes. Preferablythis time period should be within the range of from about 5 minutes upto about 60 minutes, and most suitable results are obtained when thetime period is within the range of about 15 minutes up to about 45minutes.

The application temperature or dipping temperature for the phosphatecoating solution should be within about the range of about 50 up toabout 220 F. and preferably the dipping temperature range should be fromabout up to about 210 F. Most suitable results are obtained when thistemperature range is from about 180 F. up to about 200 F.

The corrosion resistant oil which is applied to the substrate after thephosphate coating solution has been applied may be described as follows.First, any number of different corrosion resistant oils may be used forapplication to the substrate subsequent to the application of thephosphate solution, and those skilled in the art will be aware ofnumerous different corrosion resistant oils which may be used for thispurpose. Preferably this corrosion resistant oil would be of theconventional type which are known to be either dispersible oremulsifiable in water, that is, a water soluble corrosion resistant oil.This corrosion resistant oil should be one which is capable of beingused over a phosphate coating to produce a generally dry to the touchcorrosion resistant film. A particularly suitable corrosion resistantoil for this purpose is the tradename oil MetexM-685, available from theMacDermid Chemical Company. Metex 685 oil is used at a 1020% by volumeamount in water and is applied from an oil bath at an operatingtemperature most suitably within the range of about 1'15145 F. Theapplication time period for this corrosion resistant oil should mostspecifically be at an immersion time period of about 30 seconds orlonger. Another suitable oil is Northwest Seal Oil available fromNorthwest Chemical Company.

Suitable corrosion resistant oils may more specifically be described asthose oils comprising a mixture of parafiin oil, oxygenated parafiinoils, and a carbitol solvent.

The application time or immersion time in the corrosion resistant oilshould broadly be from about of a minute up to as long as is convenient.Preferably, the application time for the corrosion resistant oil shouldbe within the range of about /2 up to about minutes and most suitablythe application time period is within the range of about /2 up to about60 minutes.

The application temperature or the immersion temperature of thesubstrate in the corrosion resistant oil should broadly be within therange of about 40 F. up to as high a temperature as is convenient, andnormally this high temperature would not be more than the boiling pointtemperature of the corrosion resistant oil. Prefera bly, the applicationtemperature for the corrosion resistant oil should be within the rangeof about 85 F. up to about 200 F. and most suitably this temperatureshould be within the range of about 115 F. up to about 145 F.

The particular choice of the corrosion resistant oil which is appliedafter the phosphate coating is applied is not a critical choice 1 solong as the above criteria are generally met and no attempt will be madeherein to exhaustively define all of the various corrosion resistantoils which could be used for the purposes of this invention.

At this point it should also be stated that after the application of thecorrosion resistant oil to the substrate and the substrate is removedfrom application contact with said corrosion resistant oil, then asuflicient amount of time should be allowed to elapse before thesubstrate is taken into the next step of the method of applying amixture of solid lubricant particle dispersion and water solublecorrosion resistant oil to the substrate. As an example, this timeperiod which should be allowed to lapse should be approximately 10minutes up to about 10 hours or more. Preferably, it should be fromabout /2 hour up to 8 hours. Still further, generally stated, so long asthe minimum time period is allowed to lapse it is sufficient andthereafter the time period can be as high a magnitude as is desired.

There now follows a description of the step of applying a mixture ofsolid lubricant particle dispersion and water soluble corrosionresistant oil to the substrate.

The lubricant particle dispersion discovery in accordance with theinvention herein, there should be one in which the lubricant is selectedfrom the group consisting of graphite, molybdenum disulfide orvermiculite. Graphite is the preferred lubricant. The lubricantparticles may be used either singly or in any combination thereof.

Preferably stated, the lubricant particle dispersion should be anyaqueous dispersion containing a percent total of solids within the broadrange of about 2% up to about 95% by weight. More specifically, thepercent total solids should be within the range of about up to about 80%and most suitable results are obtained using a dispersion containingfrom about 20% up to about 50% by weight total solids.

The lubricant particle size should broadly be within the range of about0.5 up to about 200 microns. Higher particle sizes than 200 microns maybe used for certain applications. Preferably the lubricant particle sizeshould be within the range of about 1 up to about 100 microns. Morespecifically but without attempting to limit the invention, thelubricant particle size may be within the narrow range of approximately20 microns up to about 70 microns.

As discussed hereinabove the lubricant particle dispersion used incombination with a water soluble corrosion resistant oil as a mixturethereof for application to the substrate.

The weight ratio of said dispersion to said oil should generally bewithin the broad range of about 1:20 to about 20:1. Preferably theweight ratio of the lubricant particle dispersion to the water solublecorrosion resistant oil should be within the range of about 1:5 to about5: 1; and, most suitably the ratio should be within the range of about1:3 to about 3:1.

The application time period for immersion dipping or applying themixture of lubricant particle dispersion and Water soluble corrosionresistant oil to the substrate should be within the broad range of aboutA second up to about 2 hours. This application time may be longer forcertain specific products or applications. Preferably, the applicationtime period for the mixture should be within the range of about A;second up to about one hour; and, more specifically, the applicationtime period for the United States patents which disclose other suitablecorrosion-resistant oils are: 2,080,299; 2,820,723; 2,861,907 and 6mixture should be within the range of about /2 second up to about 15minutes.

The application or the dipping temperature for applying the mixture tothe substrate should broadly be within the range of about 40 F. up toabout 220 F. Preferably this temperature range should be within therange of about 70 up to about 210 F. and more specifically, thistemperature range should be from about F. up to about 145 F.

The properties obtained by substrate products coated in accordance withthis invention are as follows: First, products coated in accordance withthis invention when tested according to the salt spray test designatedASTM test B-117-61 give values of 700 to 800 hours or higher salt spraycorrosion resistance results. Products coated in accordance with theinvention herein possess an unexpectedly high lubricity or highlylubricated surface. This is indicated by the fact that fasteners coatedin accordance with this invention have prevailing torques whichprevailing torques are improved by 2550% or more at a particular givenclamp load when coated in accordance with the invention herein.

In order to further illustrate the invention the following additionalexamples are provided. It is to be understood, however, that all of theexamples in this application are included for illustrative purposes andare not intended to be limiting of the scope of the invention as setforth in the subjoined claims.

EXAMPLE 6 Threaded fasteners of the prevailing torque type known tothose skilled in the art were surface treated in accordance with theinvention herein and rendered into a high lubricity, corrosion resistantfasteners in the following manner.

First, a batch of the fasteners were cleaned in a soap bath by immersiontherein for approximately 5 minutes. The particular soap used for thiscleaning operation was not critical and any heavy duty detergent orindustrial detergent or the like may be used.

Second, the fasteners were subjected to a cold Water rinse forapproximately 30 to 60 seconds.

Third, the fasteners were immersed in an aqueous acidic metallicphosphate coating solution for approximately 30 minutes with thephosphate coating solution being maintained at a temperature ofapproximately 195 F. The coating solution used was a zinc-iron phosphatecoating solution of Phosphotex A-8 as described hereinabove.

Fourth, after removal of the fasteners from the phosphate coatingsolution the fasteners were subjected to a hot water rinse forapproximately 30 to 60 seconds at a temperature of approximately 170 F.The temperature and time period of the hot water rinse was found not tobe critical.

Fifth, the fasteners were immersed in a corrosion resistant oil for atime period of approximately 1-2 minutes with the oil temperature beingapproximately 135 F. The oil used for this particular treatment wasMetex-685 described hereinabove. Subsequent to the application of thisoil, the fasteners were removed from the oil and allowed to stand in theopen at room temperature for several hours, on a broad basis, and morespecifically for about one hour.

Sixth, the fasteners were immersed in a mixture of solid lubricantparticle dispersion and water soluble corrosion resistant oil for a timeperiod of approximately 30 seconds and at an immersion temperature ofapproximately F. The lubricant particle dispersion used was the productProdag which is an aqueous dispersion of graphite in water carrier at anapproximately 30% by weight solids content. The density of this specificdispersion in pounds per gallon is approximately 9.8. The product Prodagis available from Acheson Industries, Inc., Port Huron, Mich. The watersoluble corrosion resistant oil used in the mixture was Metex 685 asdescribed hereinabove. The weight ratio of the lubricant particledispersion to the 7 water soluble corrosion resistant oil wasapproximately 1: 1 ratio by weight.

The fastener coated in accordance with the above description was a %16 xcone lock nut of steel type 1035. This type threaded lock nut fastenerwhen so surface treated as described hereinabove, gave a salt spray testresult of 800 hours or higher. Furthermore, it was determined that theprevailing torque in inch pounds at particular clamp loads in inchpounds was improved by 2550% or higher due to the highly improvedlubricity imparted to the fastener surface, as compared to an identicalfastener coated by a conventional phosphate coating process and treatedwith corrosion resistantoil.

EXAMPLE 7 The surface treatment process of Example 6 may satisfactorilybe repeated except that in place of the graphite dispersion (Prodag) adispersion is used comprised of colloidal molybdenum disulfide in water.This molybdenum disulfide dispersion has a density of 11 pounds pergallon with the molybdenum disulfide particle size being approximately 1micron. The percent total solids of the molybdenum disulfide dispersionin the water carrier should be about 35% by weight total solids. Asuitable molybdenum disulfide dispersion is Acheson Industries, Inc.product No. 206.

EXAMPLE 8 The process of Example 6 may satisfactorily be repeated butusing instead of the graphite dispersion a dispersion of vermiculite inwater at a total solids content of about 36% by weight total solids.This vermiculite dispersion has a density of approximately 11.4 poundsper gallon. The carrier for the vermiculite dispersion is water. Asuitable vermiculite dispersion for use in carrying out this examplewould be Acheson Industries, Inc. product No. 395.

While it will be apparent that the preferred embodiments of theinvention are well calculated to fulfill the objects above stated, itwill be appreciated that the invention is susceptible to modification,variation and change without departing from the proper scope or fairmeaning of the subjoined claims.

What is claimed is:

1. A method of preparing a high lubricity, corrosion resistant, coatedfastener substrate product comprising the steps of:

cleaning the fastener substrate,

applying an aqueous acidic metallic phosphate coating solution to thesubstrate,

said coating solution being selected from at least one of the groupconsisting of zinc phosphate, manganese phosphate, or iron phosphatecoating solutions, applying a corrosion resistant oil to the substrate,and applying a mixture of solid lubricant particle dispersion and watersoluble corrosion resistant oil to the substrate,

said lubricant being selected from the group consisting of graphite,molybdenum disulfide, or vermiculite, said lubricant particle size beingfrom about 0.5

to about 200 microns,

said dispersion containing between about 2% and about 95 by weight totalsolids content, and

said mixture containing a weight ratio of said dispersion to said oilbetween about 1:20 and about 20:1.

2. The method of claim 1 wherein said particle is from about 1 to about1'00 microns.

3. The method of claim 1 wherein said dispersion contains between about5% and about total solids.

4. The method of claim 1 wherein said weight ratio is between about 1:5and about 5:1.

5. The method of claim 1 wherein said particle is from about 1 to about100 microns, said dispersion contains between about 5% and about 80%total solids, said weight ratio is between about 1:5 and about 5: 1.

6. The method of claim 1 wherein said particle is from about 1 to about100 microns, said dispersion contains between about 20% and about 50%total solids, said weight ratio is between about 1:3 and about 3: 1.

7. The method of claim 1, 2, 3, 4, 5 or 6 wherein said lubricant isgraphite.

8. A threaded fastener product comprised of a coated substrate metalhaving a first applied coating thereon of an aqueous acidic metallicphosphate coating solution,

of the group consisting of zinc phosphate,

said coating solution being selected from at least one manganesephosphate, or iron phosphate coating solutions,

having a second applied coating thereon of a corrosion resistant oil,and

having a third applied coating thereon of a mixture of solid lubricantparticle dispersion and water soluble corrosion resistant oil,

said lubricant being selected from the group consisting of graphite,molybdenum disulfide, or vermiculite, said lubricant particle size beingfrom about 0.5 to

about 200 microns, said dispersion containing between about 2% and about95% by weight total solids content, and said mixture containing a weightratio of said dispersion to said oil between about 1:20 and about 20: 1.

References Cited UNITED STATES PATENTS 1,964,671 6/1934 Nesbitt ll7l34X2,266,379 12/1941 Floyd l486.l5X 2,731,360 1/1956 Love 148-6.]5X2,899,336 8/1959 Peck 1l7l34X 3,035,926 5/1962 Larrieu l17l34X 3,297,4931/1967 Blum et a1 117-134X RALPH S. KENDALL, Primary Examiner C. WESTON,Assistant Examiner US. Cl. X.R. -32, 32.1, 35

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 573,111 Dated March 0, 1971 Inventor(s) Raymond L- Thurston It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 8, line 27, "of the group consisting of zinc phosphate, shouldhave been --said coating solution being selected from at least one--.

' Column 8, line 28, "said coating solution being selected from at leastone" should have been --of the group consistingof zinc phosphate,

Signed and sealed this 22nd day of June 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, J Attesting OfficerCommissioner of Patent FORM PO-\O50 (10-59) u co -uc 50375.

